This invention relates to torque struts which are coupled between a pair of automobile parts, normally in the area of the engine. More particularity, the invention relates to resilient elastomeric bushings which are used to dampen forces imparted to the torque struts during operation of a motor vehicle.
It is well known to form such bushings with a solid, resilient rubber insert or cushion. It is also well known to provide such inserts with large voids or cavities to vary the force dampening characteristics of the bushing, as exemplified by U.S. Pat. No. 4,685,531. Many elastomeric configurations have been used to provide vibration isolation while allowing varying degrees of engine roll. For example, some engines are allowed to move as little as plus or minus 6 mm, while other engines are allowed to move plus or minus 25 mm. The bushing of the invention meets two major design criteria; namely, it maintains acceptable stress levels during maximum loading conditions, and it maintains adequate axial push-out and alignment properties.
Briefly stated, the invention is in a torque strut bushing which comprises a resilient elastomeric insert which is between a rigid inner sleeve and a radially spaced, concentric, rigid outer sleeve in which the insert and attached inner sleeve is housed. The insert is bonded to the inner sleeve, and is provided with a number of grooves and fingers, both of which extend from the outer sleeve in the direction of the longitudinal axis of the inner sleeve and terminate in spaced relation from the inner sleeve. The grooves and fingers between them, are sized, such that the free distal ends of the fingers will flex limited distances about the longitudinal axis of the inner sleeve. A rigid, annular ring is circumferentially molded in the elastomeric material around the outer periphery of the insert midway between the opposing ends of the insert and attached inner sleeve.
The function of the grooves are two-fold; namely, they reduce radial spring rate and they increase allowable axial rotation of the resilient elastomeric insert and attached inner sleeve, since the fingers, formed between the grooves, tend to bend or flex rather than place the elastomeric insert in shear. The rigid ring provides additional axial push-out restraint and prevents misalignment of the bushing after large radial displacements. The elastomeric insert is not bonded to the outer sleeve or housing, so that it will never be placed in tension which adversely affects the durability of the insert.